realtek: thermal driver for rtl838x and rtl930x SoCs

Add simple driver reading the internal temperature sensor.

Signed-off-by: Bjørn Mork <bjorn@mork.no>
Link: https://github.com/openwrt/openwrt/pull/17967
Signed-off-by: Sander Vanheule <sander@svanheule.net>

target/linux/realtek/dts/rtl838x.dtsi

@@ -264,6 +264,11 @@
 			pinctrl-names = "default";
 			pinctrl-0 = <&mdio_aux_mdx>, <&aux_mode_mdio>;
 		};
+
+		soc_thermal: thermal {
+			compatible = "realtek,rtl8380-thermal";
+			#thermal-sensor-cells = <0>;
+		};
 	};
 
 	pinmux@1b000144 {
@@ -364,4 +369,20 @@
 		interrupt-parent = <&intc>;
 		interrupts = <20 2>;
 	};
+
+	thermal_zones: thermal-zones {
+		cpu-thermal {
+			polling-delay-passive = <1000>;
+			polling-delay = <1000>;
+			coefficients = <1000 0>;
+			thermal-sensors = <&soc_thermal>;
+			trips {
+				cpu-crit {
+					temperature = <105000>;
+					hysteresis = <2000>;
+					type = "critical";
+				};
+			};
+		};
+	};
 };

target/linux/realtek/dts/rtl930x.dtsi

@@ -156,6 +156,11 @@
 
 			status = "disabled";
 		};
+
+		soc_thermal: thermal {
+			compatible = "realtek,rtl9300-thermal";
+			#thermal-sensor-cells = <0>;
+		};
 	};
 
 	pinmux@1b00c600 {
@@ -209,4 +214,20 @@
 		interrupt-parent = <&intc>;
 		interrupts = <23 2>;
 	};
+
+	thermal_zones: thermal-zones {
+		cpu-thermal {
+			polling-delay-passive = <1000>;
+			polling-delay = <1000>;
+			coefficients = <1000 0>;
+			thermal-sensors = <&soc_thermal>;
+			trips {
+				critical {
+					temperature = <105000>;
+					hysteresis = <2000>;
+					type = "critical";
+				};
+			};
+		};
+	};
 };

target/linux/realtek/files-6.6/drivers/thermal/realtek-thermal.c

@@ -0,0 +1,146 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Realtek thermal sensor driver
+ *
+ * Copyright (C) 2025 Bjørn Mork <bjorn@mork.no>>
+ */
+
+#include <linux/bitfield.h>
+#include <linux/mfd/syscon.h>
+#include <linux/module.h>
+#include <linux/platform_device.h>
+#include <linux/regmap.h>
+#include "thermal_hwmon.h"
+
+#define RTL8380_THERMAL_METER_CTRL0	0x98
+#define RTL8380_THERMAL_METER_CTRL1	0x9c
+#define RTL8380_THERMAL_METER_CTRL2	0xa0
+#define RTL8380_THERMAL_METER_RESULT	0xa4
+#define RTL8380_TM_ENABLE		BIT(0)
+#define RTL8380_TEMP_VALID		BIT(8)
+#define RTL8380_TEMP_OUT_MASK		GENMASK(6, 0)
+
+#define RTL9300_THERMAL_METER_CTRL0	0x60
+#define RTL9300_THERMAL_METER_CTRL1	0x64
+#define RTL9300_THERMAL_METER_CTRL2	0x68
+#define RTL9300_THERMAL_METER_RESULT0	0x6c
+#define RTL9300_THERMAL_METER_RESULT1	0x70
+#define RTL9300_TM_ENABLE		BIT(16)
+#define RTL9300_TEMP_VALID		BIT(24)
+#define RTL9300_TEMP_OUT_MASK		GENMASK(23, 16)
+#define RTL9300_SAMPLE_DLY_SHIFT	(16)
+#define RTL9300_SAMPLE_DLY_MASK		GENMASK(RTL9300_SAMPLE_DLY_SHIFT + 15, RTL9300_SAMPLE_DLY_SHIFT)
+#define RTL9300_COMPARE_DLY_SHIFT	(0)
+#define RTL9300_COMPARE_DLY_MASK       	GENMASK(RTL9300_COMPARE_DLY_SHIFT + 15, RTL9300_COMPARE_DLY_SHIFT)
+
+struct realtek_thermal_priv {
+	struct regmap *regmap;
+	bool enabled;
+};
+
+static void rtl8380_thermal_init(struct realtek_thermal_priv *priv)
+{
+	priv->enabled = !regmap_update_bits(priv->regmap, RTL8380_THERMAL_METER_CTRL0, RTL8380_TM_ENABLE, RTL8380_TM_ENABLE);
+}
+
+static int rtl8380_get_temp(struct thermal_zone_device *tz, int *res)
+{
+	struct realtek_thermal_priv *priv = thermal_zone_device_priv(tz);
+	int offset = thermal_zone_get_offset(tz);
+	int slope = thermal_zone_get_slope(tz);
+	u32 val;
+	int ret;
+
+	if (!priv->enabled)
+		rtl8380_thermal_init(priv);
+
+	ret = regmap_read(priv->regmap, RTL8380_THERMAL_METER_RESULT, &val);
+	if (ret)
+		return ret;
+
+	if (!(val & RTL8380_TEMP_VALID))
+		return -EAGAIN;
+
+	*res = FIELD_GET(RTL8380_TEMP_OUT_MASK, val) * slope + offset;
+	return 0;
+}
+
+static const struct thermal_zone_device_ops rtl8380_ops = {
+	.get_temp = rtl8380_get_temp,
+};
+
+static void rtl9300_thermal_init(struct realtek_thermal_priv *priv)
+{
+	/* increasing sample delay makes get_temp() succeed more often */
+	regmap_update_bits(priv->regmap, RTL9300_THERMAL_METER_CTRL1, RTL9300_SAMPLE_DLY_MASK, 0x0800 << RTL9300_SAMPLE_DLY_SHIFT);
+	priv->enabled = !regmap_update_bits(priv->regmap, RTL9300_THERMAL_METER_CTRL2, RTL9300_TM_ENABLE, RTL9300_TM_ENABLE);
+}
+
+static int rtl9300_get_temp(struct thermal_zone_device *tz, int *res)
+{
+	struct realtek_thermal_priv *priv = thermal_zone_device_priv(tz);
+	int offset = thermal_zone_get_offset(tz);
+	int slope = thermal_zone_get_slope(tz);
+	u32 val;
+	int ret;
+
+	if (!priv->enabled)
+		rtl9300_thermal_init(priv);
+
+	ret = regmap_read(priv->regmap, RTL9300_THERMAL_METER_RESULT0, &val);
+	if (ret)
+		return ret;
+	if (!(val & RTL9300_TEMP_VALID))
+		return -EAGAIN;
+
+	*res = FIELD_GET(RTL9300_TEMP_OUT_MASK, val) * slope + offset;
+	return 0;
+}
+
+static const struct thermal_zone_device_ops rtl9300_ops = {
+	.get_temp = rtl9300_get_temp,
+};
+
+static int realtek_thermal_probe(struct platform_device *pdev)
+{
+	struct realtek_thermal_priv *priv;
+	struct thermal_zone_device *tzdev;
+	struct device *dev = &pdev->dev;
+	struct regmap *regmap;
+
+	priv = devm_kzalloc(dev, sizeof(*priv), GFP_KERNEL);
+	if (!priv)
+		return -ENOMEM;
+
+	regmap = syscon_node_to_regmap(dev->of_node->parent);
+	if (IS_ERR(regmap))
+		return PTR_ERR(regmap);
+
+	priv->regmap = regmap;
+	tzdev = devm_thermal_of_zone_register(dev, 0, priv, device_get_match_data(dev));
+	if (IS_ERR(tzdev))
+		return PTR_ERR(tzdev);
+
+	return devm_thermal_add_hwmon_sysfs(dev, tzdev);
+}
+
+static const struct of_device_id realtek_sensor_ids[] = {
+	{ .compatible = "realtek,rtl8380-thermal", .data = &rtl8380_ops, },
+	{ .compatible = "realtek,rtl9300-thermal", .data = &rtl9300_ops, },
+	{ /* sentinel */ }
+};
+MODULE_DEVICE_TABLE(of, realtek_sensor_ids);
+
+static struct platform_driver realtek_thermal_driver = {
+	.probe	= realtek_thermal_probe,
+	.driver	= {
+		.name		= "realtek-thermal",
+		.of_match_table	= realtek_sensor_ids,
+	},
+};
+
+module_platform_driver(realtek_thermal_driver);
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Bjørn Mork <bjorn@mork.no>");
+MODULE_DESCRIPTION("Realtek temperature sensor");

target/linux/realtek/patches-6.6/330-add-realtek-thernal-driver.patch

@@ -0,0 +1,21 @@
+--- a/drivers/thermal/Kconfig
++++ b/drivers/thermal/Kconfig
+@@ -522,4 +522,11 @@ config LOONGSON2_THERMAL
+ 	  is higher than the high temperature threshold or lower than the low
+ 	  temperature threshold, the interrupt will occur.
+ 
++config REALTEK_THERMAL
++	tristate "Realtek RTL838x and RTL930x thermal sensor support"
++	depends on RTL838X || RTL930X || COMPILE_TEST
++	depends on THERMAL_OF
++	help
++	  Support thermal sensor in Realtek RTL838x and RTL930x SoCs
++
+ endif
+--- a/drivers/thermal/Makefile
++++ b/drivers/thermal/Makefile
+@@ -64,3 +64,4 @@ obj-$(CONFIG_AMLOGIC_THERMAL)     += aml
+ obj-$(CONFIG_SPRD_THERMAL)	+= sprd_thermal.o
+ obj-$(CONFIG_KHADAS_MCU_FAN_THERMAL)	+= khadas_mcu_fan.o
+ obj-$(CONFIG_LOONGSON2_THERMAL)	+= loongson2_thermal.o
++obj-$(CONFIG_REALTEK_THERMAL)	+= realtek-thermal.o

target/linux/realtek/rtl838x/config-6.6

@@ -210,6 +210,7 @@ CONFIG_REALTEK_OTTO_TIMER=y
 CONFIG_REALTEK_OTTO_WDT=y
 CONFIG_REALTEK_PHY=y
 CONFIG_REALTEK_SOC_PHY=y
+CONFIG_REALTEK_THERMAL=y
 CONFIG_REGMAP=y
 CONFIG_REGMAP_I2C=y
 CONFIG_REGMAP_MDIO=y
@@ -237,6 +238,14 @@ CONFIG_SYS_SUPPORTS_BIG_ENDIAN=y
 CONFIG_SYS_SUPPORTS_HIGHMEM=y
 CONFIG_SYS_SUPPORTS_MIPS16=y
 CONFIG_TARGET_ISA_REV=2
+CONFIG_THERMAL=y
+CONFIG_THERMAL_DEFAULT_GOV_STEP_WISE=y
+# CONFIG_THERMAL_DEFAULT_GOV_FAIR_SHARE is not set
+# CONFIG_THERMAL_DEFAULT_GOV_USER_SPACE is not set
+CONFIG_THERMAL_EMERGENCY_POWEROFF_DELAY_MS=0
+CONFIG_THERMAL_GOV_STEP_WISE=y
+CONFIG_THERMAL_HWMON=y
+CONFIG_THERMAL_OF=y
 CONFIG_TICK_CPU_ACCOUNTING=y
 CONFIG_TIMER_OF=y
 CONFIG_TIMER_PROBE=y

target/linux/realtek/rtl930x/config-6.6

@@ -188,6 +188,7 @@ CONFIG_REALTEK_OTTO_TIMER=y
 CONFIG_REALTEK_OTTO_WDT=y
 CONFIG_REALTEK_PHY=y
 CONFIG_REALTEK_SOC_PHY=y
+CONFIG_REALTEK_THERMAL=y
 CONFIG_REGMAP=y
 CONFIG_REGMAP_I2C=y
 CONFIG_REGMAP_MDIO=y
@@ -216,6 +217,14 @@ CONFIG_SYS_SUPPORTS_HIGHMEM=y
 CONFIG_SYS_SUPPORTS_MIPS16=y
 CONFIG_SYS_SUPPORTS_MULTITHREADING=y
 CONFIG_TARGET_ISA_REV=2
+CONFIG_THERMAL=y
+CONFIG_THERMAL_DEFAULT_GOV_STEP_WISE=y
+# CONFIG_THERMAL_DEFAULT_GOV_FAIR_SHARE is not set
+# CONFIG_THERMAL_DEFAULT_GOV_USER_SPACE is not set
+CONFIG_THERMAL_EMERGENCY_POWEROFF_DELAY_MS=0
+CONFIG_THERMAL_GOV_STEP_WISE=y
+CONFIG_THERMAL_HWMON=y
+CONFIG_THERMAL_OF=y
 CONFIG_TICK_CPU_ACCOUNTING=y
 CONFIG_TIMER_OF=y
 CONFIG_TIMER_PROBE=y